FIG. 20 shows the structure of a drive circuit of a passive-matrix type liquid crystal display apparatus disclosed in Japanese Publication for Unexamined Patent Application (Tokukaihei) No. 6-18848 (1994). In this structure, two analog switches are provided for each segmented electrode Yi (i=1 to m). For instance, when an analog switch 261 connected to a segmented electrode Y.sub.1 is turned ON, a voltage V.sub.3 is applied to the segmented electrode Yi. In other cases, an analog switch 241 is turned ON, and a voltage V.sub.1 is applied to the segmented electrode Yi.
FIG. 21 shows a drive circuit on the source side of an active-matrix type liquid crystal display apparatus disclosed in Japanese Publication for Unexamined Patent Application (Tokukaihei) No. 5-100635 (1993). In this drive circuit structure, a voltage to be applied to the active-matrix type liquid crystal display apparatus is determined by selecting a power source from external power sources V0 to V7 according to the values of high order bits D1 to D3 of data retained in a latch circuit 201, and by turning ON/OFF an analog switch 206 according to the values of low order bits D4 and D5 and a timing control signal 209.
FIGS. 22 and 19 are block diagrams showing examples of the structure of a drive circuit of a conventional ferroelectric liquid crystal display apparatus and the waveforms of drive voltages. A drive circuit 71 on the scanning side, for driving scanning electrodes L, includes a shift register 76 and an analog switch array 77. The drive circuit 71 selects one voltage waveform from three voltage waveforms, V.sub.CA, V.sub.CB and V.sub.CC, shown in FIG. 19, based on the value of input two-bit data YI, and applies the selected waveform to the scanning electrodes.
A drive circuit 72 on the segment side, for driving segmented electrodes S, includes a shift register 73, a latch 74, and an analog switch array 75. The drive circuit 72 selects one voltage waveform from two voltage waveforms, V.sub.SD and V.sub.SE, shown in FIG. 19, based on data XI retained in the latch 74, and applies the selected waveform to the segmented electrodes.
FIG. 23 shows an example of the waveforms used by a drive scheme for a ferroelectric liquid crystal display apparatus, which was suggested by the present inventors and disclosed in Japanese Publication for Unexamined Patent Application (Tokukaihei) No. 8-50278 (1996). In this drive scheme, a multiple gray scale display is achieved with a ferroelectric liquid crystal display apparatus by forming one pixel from three sub-pixels A.sub.ijA, A.sub.ijB and A.sub.ijC which are driven by three lines of scanning electrodes L.sub.iA, L.sub.iB and L.sub.iC (i=0, 1, . . . ), and one line of segmented electrode S.sub.j (j=0, 1, . . . ) as shown in FIG. 11, and by applying different selection voltage waveforms V.sub.CA, V.sub.CB and V.sub.CC shown in FIG. 23, to the three lines of scanning electrodes, respectively.
However, the above-mentioned conventional structure suffers from the following drawbacks.
In the drive circuit on the segment side of the conventional passive-matrix type liquid crystal display apparatus, two analog switches are required for one output level of each output terminal. When forming the drive circuit as an integrated circuit, if the number of output terminals and the area of a chip are fixed, the area for each analog switch can be increased by decreasing the number of analog switches per output terminal, and the output resistance of each output terminal can be reduced by an amount corresponding to the increase.
The technique disclosed in Japanese Publication for Unexamined Patent Application (Tokukaihei) No. 5-100635 (1993) above is a technique for decreasing the number of analog switches per output terminal in the drive circuit on the source side of the active-matrix type liquid crystal display apparatus. However, a scheme to obtain a plurality of output levels using one analog switch as a drive circuit of a passive-matrix type liquid crystal display apparatus has not yet been proposed.
A conventional ferroelectric liquid crystal display apparatus achieves bright and dark displays by using bistability of ferroelectric liquid crystals and aligning the molecule long axis of a ferroelectric liquid crystal molecule in one of the stable states with the polarization axis of a polarizing plate. With the use of ferroelectric liquid crystals with negative dielectric anisotropy, the memory angle changes depending on the root-mean-square value of a bias voltage applied, and the memory angle becomes larger with an increase in the root-mean-square value.
For example, in the drive scheme disclosed in Japanese Publication for Unexamined Patent Application (Tokukaihei) No. 8-50278 (1996) above, four kinds of voltage waveforms are applied to the segmented electrodes, and a variation of the root-mean-square value of the bias voltage is relatively wide. Therefore, even when the polarizing plate is positioned according to one bias state, if the display pattern changes into another bias state, the memory angle changes and the contrast is lowered.
The memory angle of the ferroelectric liquid crystal also changes depending on temperature. Therefore, even when the polarization axis of the polarizing plate is positioned according to a memory angle at a certain temperature, the memory angle varies as the temperature changes, and the contrast is lowered.